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author | Eric Dumazet <eric.dumazet@gmail.com> | 2011-09-19 05:52:27 +0000 |
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committer | David S. Miller <davem@davemloft.net> | 2011-09-28 13:29:50 -0400 |
commit | 16e5726269611b71c930054ffe9b858c1cea88eb (patch) | |
tree | 50d25ec97d639b418964bad2f45774d657468c74 /net/unix/af_unix.c | |
parent | a9e9fd7182332d0cf5f3e601df3e71dd431b70d7 (diff) | |
download | linux-stable-16e5726269611b71c930054ffe9b858c1cea88eb.tar.gz linux-stable-16e5726269611b71c930054ffe9b858c1cea88eb.tar.bz2 linux-stable-16e5726269611b71c930054ffe9b858c1cea88eb.zip |
af_unix: dont send SCM_CREDENTIALS by default
Since commit 7361c36c5224 (af_unix: Allow credentials to work across
user and pid namespaces) af_unix performance dropped a lot.
This is because we now take a reference on pid and cred in each write(),
and release them in read(), usually done from another process,
eventually from another cpu. This triggers false sharing.
# Events: 154K cycles
#
# Overhead Command Shared Object Symbol
# ........ ....... .................. .........................
#
10.40% hackbench [kernel.kallsyms] [k] put_pid
8.60% hackbench [kernel.kallsyms] [k] unix_stream_recvmsg
7.87% hackbench [kernel.kallsyms] [k] unix_stream_sendmsg
6.11% hackbench [kernel.kallsyms] [k] do_raw_spin_lock
4.95% hackbench [kernel.kallsyms] [k] unix_scm_to_skb
4.87% hackbench [kernel.kallsyms] [k] pid_nr_ns
4.34% hackbench [kernel.kallsyms] [k] cred_to_ucred
2.39% hackbench [kernel.kallsyms] [k] unix_destruct_scm
2.24% hackbench [kernel.kallsyms] [k] sub_preempt_count
1.75% hackbench [kernel.kallsyms] [k] fget_light
1.51% hackbench [kernel.kallsyms] [k]
__mutex_lock_interruptible_slowpath
1.42% hackbench [kernel.kallsyms] [k] sock_alloc_send_pskb
This patch includes SCM_CREDENTIALS information in a af_unix message/skb
only if requested by the sender, [man 7 unix for details how to include
ancillary data using sendmsg() system call]
Note: This might break buggy applications that expected SCM_CREDENTIAL
from an unaware write() system call, and receiver not using SO_PASSCRED
socket option.
If SOCK_PASSCRED is set on source or destination socket, we still
include credentials for mere write() syscalls.
Performance boost in hackbench : more than 50% gain on a 16 thread
machine (2 quad-core cpus, 2 threads per core)
hackbench 20 thread 2000
4.228 sec instead of 9.102 sec
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/unix/af_unix.c')
-rw-r--r-- | net/unix/af_unix.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c index ec68e1c05b85..466fbcc5cf77 100644 --- a/net/unix/af_unix.c +++ b/net/unix/af_unix.c @@ -1381,8 +1381,10 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb) static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool send_fds) { int err = 0; + UNIXCB(skb).pid = get_pid(scm->pid); - UNIXCB(skb).cred = get_cred(scm->cred); + if (scm->cred) + UNIXCB(skb).cred = get_cred(scm->cred); UNIXCB(skb).fp = NULL; if (scm->fp && send_fds) err = unix_attach_fds(scm, skb); @@ -1392,6 +1394,24 @@ static int unix_scm_to_skb(struct scm_cookie *scm, struct sk_buff *skb, bool sen } /* + * Some apps rely on write() giving SCM_CREDENTIALS + * We include credentials if source or destination socket + * asserted SOCK_PASSCRED. + */ +static void maybe_add_creds(struct sk_buff *skb, const struct socket *sock, + const struct sock *other) +{ + if (UNIXCB(skb).cred) + return; + if (test_bit(SOCK_PASSCRED, &sock->flags) || + !other->sk_socket || + test_bit(SOCK_PASSCRED, &other->sk_socket->flags)) { + UNIXCB(skb).pid = get_pid(task_tgid(current)); + UNIXCB(skb).cred = get_current_cred(); + } +} + +/* * Send AF_UNIX data. */ @@ -1538,6 +1558,7 @@ restart: if (sock_flag(other, SOCK_RCVTSTAMP)) __net_timestamp(skb); + maybe_add_creds(skb, sock, other); skb_queue_tail(&other->sk_receive_queue, skb); if (max_level > unix_sk(other)->recursion_level) unix_sk(other)->recursion_level = max_level; @@ -1652,6 +1673,7 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock, (other->sk_shutdown & RCV_SHUTDOWN)) goto pipe_err_free; + maybe_add_creds(skb, sock, other); skb_queue_tail(&other->sk_receive_queue, skb); if (max_level > unix_sk(other)->recursion_level) unix_sk(other)->recursion_level = max_level; |